Users of touchscreen-based devices (such as tablets and smartphones) are often frustrated by the devices' limited ability to differentiate between different kinds of touches and to respond in unexpected ways to stray touches. Additionally, when users view these devices at unusual angles (e.g., from the extreme right or left of the device), touch accuracy is compromised by the parallax effect, in which the desired location of touch does not align with the actual location of touch. These performance limitations may significantly reduce a user's quality of experience with touchscreen devices.